Revenue management generally includes attempting to maximize revenue through differential pricing and inventory control when selling a product or service. Revenue management may be relatively straightforward when it comes to airline tickets, hotel rooms, or rental cars, where the unit of sale is usually a single ticket, a single room, a single car, or at most a few units. However, advertisement slots, particularly for television, are usually requested, bought, and sold in various groupings. Therefore, revenue management for advertisements may require different techniques to maximize revenue.